DE2527069B2 - oil soaked electrical device - Google Patents

Description

The invention relates to oil-soaked electrical devices having at least two electrodes and at least one film of a polyolefin comprising structural element with an arylalkane compound containing mixture is impregnated.

As an insulating oil for capacitors, transformers, cables etc. is usually used extensively mineral oil-like insulating oils and chlorinated diphenyl oils. The requirement for increased high voltage load capacity and the small size of electrical devices meant that these oils have recently been used in combination with plastic materials, in particular with polyolefins had to. Compared to the conventional use in connection with paper, the application In combination with plastics, an improvement in the insulation properties can be achieved, but to a limited extent this is a corresponding suitability of the oils, whereby the following problem arises for the conventional oils signed:

(1) The plastic materials are easily attacked by the oils through dissolution, especially polyolefin materials, so that the insulation effect is impaired.

(2) The initial partial discharge voltage is low, and once a discharge has occurred, the discharge area increases in order not to heal afterwards. The lifespan therefore falls because of the discharge aging very briefly.

(3) Chlorinated compounds generate free as a result of discharge and heat aging processes Chlorine, which reduces the insulation effect.

In general, the reliability of oil-impregnated electrical devices is closely related to the Corona properties together. For devices that use conventional insulating oils when corona discharges occur, the insulating

T materials and the insulating oils in the field of Discharge is decomposed by the discharge energy, and the decomposition products and gases facilitate corona discharge still further, whereby the corona discharge energy continues to increase and that caused by the corona discharge conditional deterioration is accelerated to eventually lead to breakdowns.

According to US-PS 38 12 407 it is already known Use aralkyl compounds as impregnating agents, However, these connections alone are not able to eliminate the difficulties mentioned (cf.Fig. 4 for Time characteristics of the corona discharge power).

From US-PS 37 96 934 is a mixture of arylalkane compound and diarylsulfone compound for Impregnation is known. However, even when impregnated with this mixture, the discharge power increases and finally leads to breakdowns (cf. the time characteristic of the corona discharge power in FIG. 7).

According to US-PS 22 82 937, Kraft paper is used as a dielectric to inhibit corrosion with a phosphoric acid ester with the addition of an acidic phosphoric acid ester or a compound which able to release the phosphoric acid residue, impregnated. However, when using a polyolefin film, this leads to particularly a polypropylene film, to one

jo deterioration in the insulating properties of the film and too accelerated degradation, as a result of which the service life of such devices is extremely shortened (cf.

Fig. 8th).

According to US Pat. No. 1,895,376, phosphoric acid ester is used alone, so this teaching cannot once the inhibiting effect of US-PS 38 12 407 can be achieved.

The object of the invention is to use a combination of plastic materials and optimally suitable oils to create electrical devices of high power density and high reliability as impregnating agents.

This goal is achieved by the oil-soaked electrical devices of the type mentioned above with a component comprising at least 2 electrodes and at least one film of a polyolefin which is impregnated with a mixture containing an arylalkane compound, characterized in that the Mixture also contains phosphate or phosphite as an organic phosphorus compound. That power

so at least 10 percent by volume and up to 80 percent by volume of the mixture, preferably 20 to 70 percent by volume, and preferably has a dielectric constant from 4 to 8 on. The aromatic content of the arylalkane compound amounts to 50 to 90% and refers here to the percentage of those carbon atoms that have aromatic rings such as form a benzene ring or a naphthalene ring, based on the total number of carbon atoms in the structure of the insulating oil molecule are involved.

The arylalkane compounds used in the invention are generalized by the following To represent formula:

where Ri is methylene,!,! - ethylene or 1,2-ethylene

draws, so

-CH, -CH ₃
—CH-

or —CH, -CH, -

R ₄ -O

\
R ₅ -OP = O

respectively.

R ₄ O

\
R ₅ OP

In these formulas it concerns the groups R4. Rs and Rb, which can be the same or different, around phenyl groups, around phenyl groups substituted with alkyl groups having 1 to 3 carbon atoms or to alkyl groups having 1 to 8 carbon atoms, such as

while R2 and Rj denote alkyl groups having 1 to 8 carbon atoms, such as CHr, C2H5-, CjH7- etc., where η = 1 to 3.

The phosphates and phosphites used in the context of the invention have the general formulas

CH ₃

QH ₁₇ - etc.

CH ₃

Examples of the oils and conventional oils used in the invention are as follows Tables 1 and 2 compiled.

Table I.
Hydrocarbon compounds

No. description Dibenzyltoluene Alkylbenzene Aromatic content boiling point Pour point Dielek Dialkyldiphenyl mineral oil tricity Triarylethane Paraffin oil % C. C. constant Oils according to the invention Diarylethane Polybutene 1 Conventional oils 86 390 -35 2.6 2 5 75 280-300 -30 2.5 3 6th 70 370-380 -15 2.4 4th 7th 60 290-300 -50 2.6 8th 37 280-300 ~ 32.5 2.3 10 270-300 -37.5 2.2 0 312-403 -12.5 2.1 0 300-400 -50 2.0

Table 2

Organic phosphorus compounds

No. description Triecresyl phosphate Tricresyl phosphite Dielek Cresyl diphenyl phosphate Trioctyl phosphite tricity Octyl diphenyl phosphate Trixylenyl phosphite constant Phosphates Trixylenyl phosphate Triphenyl phosphite 9 Trioctyl phosphate 7.0 10 Triisopropyl phenyl phosphate '$ 1 11th Phosphites 8.0 12th 15th 6.0 13th 16 4.5 14th 17th 7.5 18th 6.5 4.0 5.5 6.0

If η in the general formula of the arylalkane compounds has the value zero, then the »» ·· "arylalkane compounds impart a strong swelling capacity and the like

have a high dissolving power for the polyolefin film, so that the spaces between the film layers become smaller, and therefore the components cannot be sufficiently soaked with them. If η is 4 or more, the compounds have a high viscosity and sufficient impregnation of the polyolefin film is not possible in this case either.

Fig. 1 is a graph showing the results of solubility tests carried out with polypropylene film in oils at elevated temperature. How out of this As shown in the graph, the solubility increased with the increase in the blending ratio the organic phosphorus compound in the oil, whereas the solubility with decreasing aromatic content the arylalkane compound increased.

FIG. 2 is a graphic representation which shows the difference between the value of tg <5 (dielectric loss factor) and the admixture ratio of the organic phosphorus compound. existing relationships. The illustration shows that there is a tendency to increase the The value of tgo with increasing admixture ratio of the organic phosphorus compound shows and that tg <Ü

especially when this ratio exceeds 80 percent.

The graph of FIG. 3 gives the difference between the corona ignition voltage and the admixture ratio the organic phosphorus compound and the aromatic content of the arylalkane compound existing relationships again. As the graph shows, it was a sufficient one The effect can be observed if one considers the corona ignition voltage in the case of an admixture ratio of 0 Percent equals 1. If the aromatic content of the arylalkane compounds was less than 50 percent, so this effect was very little, and some of these compounds were with the organic phosphorus compounds not compatible. The arylalkane compounds with an aromatic content of less than 50 Percent were therefore not suitable. Was the aromatic content of the arylalkane compounds on the other hand higher than 90 percent, the vapor pressure of the compounds assumed high values and, conversely, increased the pour point is above normal temperature, so that the characteristic properties of an oil then were not sufficiently pronounced.

From the findings illustrated in FIGS. 1, 2 and 3 it follows that those mixtures on are most suitable, the an arylalkane compound with an aromatic content of 50 to 90 percent and a Contains 20 to 70 percent of an organic phosphorus compound.

The following exemplary embodiments serve to further illustrate the invention.

Embodiment 1

A capacitor of 1 kVA was manufactured by using capacitor components in the form of aluminum foils as Electrodes and polypropylene film were impregnated as a dielectric with an impregnating agent, which consists of a Mixture of a diarylethane (for example 1,1-phenylxylylethane) with tricresyl phosphate in a volume ratio of 2 to 1. In addition, a capacitor was the same construction, its K'jndensatorbauteile but were only soaked with the diarylethane. The change over time was observed in these capacitors the corona discharge power measured. The measurement results are shown in FIG. The initial one Corona discharge power was set equal to 1, and as can be seen from Fig. 4, it decreased Discharge power in the case of the capacitor according to the invention in the course of a few minutes, and a dielectric breakdown did not occur, whereas the discharge performance only increased with the Arylalkane compound soaked capacitor increased, followed by dielectric breakdown took place. Similar effects have also been achieved with other phosphorus compounds, depending on the Type of device and capacity were used under optimal conditions. Noticeable effects can be produced especially when the potential vessel over the insulator has a value of 30 V / μ exceeded.

Since in the production of organic phosphorus compounds, for example of phosphates and phosphites, If chlorine compounds are used, free chlorine may be present. One can therefore go to the elimination the free chlorine and add an epoxy compound to increase the service life, which is beneficial affects. Examples of such F.poxy compounds are dinentendioxni. Bi.s (2.3) c |> oxycyclobcnzy lather, Di (I? - ethylhexyl) -4,5-epoxycyclohexane-1,2-dicarboxylic acid ester, an epoxy compound modified with soybean oil etc. The proportion of the epoxy compound added is expediently 0.05 to 5

'■> percent by weight. If this proportion exceeds 5 percent, the addition acts in the opposite sense as an impurity, and the tgo characteristic deteriorates, while a proportion of less than 0.0f percent has practically no effect.

H) As part of the inventive efforts, it was also possible to clarify that the phosphoric acid esters also contain a small proportion of acidic phosphoric acid esters and that thereby the chain reactor of radical decay in plastic materials such as

r> polypropylene films is accelerated, whereupon as a result the thermal self-polymerization reaction takes place a conversion into polyphosphoric acid, which is a Aging of the plastic materials and the insulating oil entails. To prevent this undesirable

2i) The course of the reaction has the addition of a radical eliminator proved to be very useful, examples of which are listed in Table 3.

Table 3

description

More suitable
Proportion. Weight percent

κι (1) Diphenylamine 1-3

(2) Phenyl-a-naphthylamine 1-3

(3) PhenyN / f-naphthylamine 1-5

(4) Diphenyl-p-phenylenediamine 0.5-10

(5) Ν, Ν'-phenylcyclohexyl-p- 5-10
5j phenylenediamine

(6) p-Oxyphenylcyclohexane 0.5-1

(7) Di-p-oxyphenylcyclohexane 0.5-1

(8) Dicresylpropane 0.5-1

(9) 2,6-di-t-butyl-4-methylphenol 0.5-5
(10) 2,4,6-tri-t-butylphenol 0.5-5

(! 1) Ul'-methylenebis (4-hydroxy-2 _: 5- 0.5-1

t-butylphenol)

(12) 2,6 '(2-t -Butyl-4-methyl-6-methyl-0.5-1

phenol) -p-cresol
4-> (13) 1,3,5-trimethyl-2,4,6-tris (3,5-di-t-0.5-1

butyl-4-oxybenzyl) benzene

(14) 2,2'-thio-bis (4-methy! -6-t-0.5-5
butylphenol)

(15) 4,4'-thio-bis (3-methyl-6-t-0.5-5
■> o butylphenol)

F i g. Fig. 5 is a graph showing the relationship between the proportion of the radical eliminator! and the length of time that elapses before a be

· -, =, elevated temperature in polypropylene film left in oil at a voltage corresponding to 90 percent of the initial breakdown voltage, sleep through takes place. As can be seen from the graph, the induction time for degradation fell far longer

ho from when the radical eliminator along with dei Epoxy compound was used.

Embodiment 2

A capacitor was made by placing dk

h ', capacitor components which were provided with a polypropylene film as a dielectric, with an impregnation mixture of diarylethane and cresyldiphenylphospha in a mixing ratio of 2 to 1 with the addition of 1

Weight percent dipentene oxide and 1 weight percent

1,3,5-trimethyl-2,4,6-tris- (3,5-di-t-butyl-4-oxybenzyl) benzene. In addition, a capacitor of the same design was manufactured, although the impregnating agent in this case did not contain the last two additives mentioned. A service life test was carried out with these capacitors by applying ^{an overvoltage in an environment with a temperature of 80 c} C, which produced the results shown in FIG. As can be seen from FIG. 6, if the additives were omitted, a dielectric breakdown occurred within 1000 hours, whereas proper capacitor operation was still possible even after 10,000 hours if the additives were provided. Corresponding results could also be achieved with other additives.

In addition, there is an additional effect in improving the flame resistance of the oil to be determined, and operational safety is thus also served to an excellent degree. When applying the oxygen index method resulted in the following classification: silicone oil 29%> Cresyl diphenyl phosphate

28%> diarylethane + cresyl diphenyl phosphate (in a volume ratio of 1 to 2) 25% > Diarylethane + cresyldiphenylphosphate (in a volume ratio of 2 to 1) 23%> Diarylethane 20% > Alkylbenzene 18% «Mineral oil 18%> Polypropylene film 17.5%.

F i g. 7 shows a time characteristic of corona discharge power a capacitor with an impregnation of a mixture of diarylethane and phenylxylylsulfone according to US-PS 37 96 934 and according to the invention. The fundamental difference between both solutions are shown in eye-catching

F i g. Fig. 8 shows the relationship between the life of a capacitor with polypropylene as the only one Dielectric, impregnated with a mixed oil of tricresyl phosphate and diarylethane, so according to the invention, however, an acidic phosphoric acid ester (monocresyl phosphate) according to the US-PS 22 82 937 was added. It was found that when an amount of acidic phosphoric acid ester was added over 1000 ppm (0.1%) the service life decreased significantly.

In addition 8 sheets of drawings

Claims (6)

Patent claims: 1. Oil-soaked electrical device having at least two electrodes and at least one Film of a polyolefin comprising component, which with an arylalkane compound containing Mixture is impregnated, characterized that the mixture also contains phosphate or phosphite as an organic phosphorus compound contains. 2. Oil-soaked electrical device according to claim 1, characterized in that the Mixture contains 10 to 80 percent by volume of the organic phosphorus compound. 3. Oil-soaked electrical device according to claim 2, characterized in that the Mixture contains 20 to 70 percent by volume of the organic phosphorus compound. 4. Oil-soaked electrical device according to one of claims 1 to 3, characterized in that that the organic phosphorus compound has a dielectric constant of 4 to 8. 5. Oil-soaked electrical device according to one of claims 1 to 4, characterized in that that the organic phosphorus compound tricresyl phosphate, cresyl diphenyl phosphate, trixylenyl phosphate or triisopropylphenyl phosphate. 6. Oil-soaked electrical device according to one of claims 1 to 5, characterized in that that the mixture additionally contains 0.05 to 5 percent by weight of an epoxy compound.